Unspecified Style point: obj.is_a? vs obj.class == Class

Although the case equality operator === is mentioned, of the two methods of class checking demonstrated here:

"this string".is_a? String  # => true
"this string".is_a? Object  # => true
4.is_a? Object              # => true

"this string".class == CSV  # => false
4.class == Fixnum           # => true
4.class == String           # => false

Neither are stated as preferred. I think it's fairly well agreed that is_a? is the the more Ruby way of doing things, but I've seen obj.class == Classname fairly often as well and it's easily readable.

The issue names no file or test; start by locating the style-guide section containing these class-checking examples and review the existing discussion. Done means the guide explicitly states whether is_a? or obj.class == Classname is preferred, or clearly documents when each is appropriate.